The invention relates to an improvement in an apparatus for nondestructive testing of base metals, welds and localized repair areas utilizing dry magnetic particles.
In equipment fabricated for highly specialized requirements, it is essential that base metals, welds and localized repair areas be inspected for continuity of material to insure the integrity of the structure. In surface testing, prods are applied to the surface to be tested so that good electrical contact is made. However, with the use of manually held prods great care must be taken to obtain good electrical contact. This is true because poor electrical contact will result in arcing and possible burning of the finished machined surface as well as a reduction in the amount of current passed through the part being tested. In the past, the prods were positioned on the part under test while applying pressure to the prods. However, it is not uncommon to find that when the power switch is turned on the prods are not making good or firm contact with the part. As a result an arc strike occurs. Also, if a manually held prod is removed from the part under test before the power switch is released, an arc strike will occur. In either case the arc strike severally mars the surface of the part under test which will require repair and refinishing.